UWB technologies have attracted attention as communication technologies in recent years. Although these technologies use extremely broad frequency bands, they are extremely low in power spectral density and therefore have the advantage of being able to share frequencies already in use. Moreover, they have advantages such as that by using short pulses of several hundred picoseconds or shorter, they make it possible to perform high-resolution position detection and the like.
In conventional microwave/milliwave band UWB technology, a pulse radar device is configured with a signal generator, wideband filter and wideband antenna each connected using a transmission line (see, for example, Non-patent Document 1 and Non-patent Document 2).
[Non-patent Document 1] Ian Gresham, “Ultra-Wideband Radar Sensors for Short-Range Vehicular Applications”, MTT VOL. 52, No. 9, pp. 2111-2113, September 2004
[Non-patent Document 2] Yoichi Kawano, Yasuhiko Nakasha, Kaoru Yokoo, Satoshi Masuda, Tsuyoshi Takahashi, Tatsuya Hirose, Yasuyuki Oishi, and Kiyoshi Hamaguchi, “An RF Chipset for Impulse Radio UWB Using 0.13 μm InP-HEMT Technology”, MTT-S Int. Microwave Symp. 2006 Digest pp. 316-319
The antenna of the pulse radar device in the prior art UWB technologies set forth in these Non-patent Document 1 and Non-patent Document 2 is either provided as a separate transmitting antenna and receiving antenna or as a shared receiving and transmitting antenna that is switched between transmit and receive by a switch. Moreover, as regards generation of the high-frequency pulse signals of the pulse radar device in these prior art UWB technologies, the configuration is either by the method using an ultra-wideband filter circuit to pass only a certain part of the frequency components of a base band signal (monopulse signal or step signal generated in accordance with the base band signal) or by the method of modulating the output of a CW signal oscillator such as by passing/blocking it in a high-speed RF switch.
On the other hand, there has also been proposed a pulse radar device wherein an RF circuit having a frequency mixer, a transmit oscillator, and a local receive oscillator is constituted by a single diode (Gunn diode or IMPATT diode) in the cavity of a waveguide and the output flange of the cavity is directly connected to the antenna unit (see, for example, Patent Document 1).
[Patent Document 1] Japanese Patent No. 3343674